Water repellent compositions

Abstract

 An aqueous emulsion composition suitable for treating cellulosic or masonry surfaces to render them water repellent is disclosed. This composition comprises (i) an alkoxysilane of the formula R_nSi(OR')_4-n wherein R is an alkyl radical, an alkenyl radical, phenyl, chloropropyl or trifluoropropyl, n is 1 or 2 and R' is an alkyl radical having 1 to 6 carbon atoms; (ii) a silane coupling agent of the formula R''_mR'''_pSi(OR')_4-m-p wherein R'' is selected from the group consisting of amino or quaternary ammonium organofunctional groups, R''' is an alkyl radical having 1 to 4 carbon atoms, R' has its previously defined meaning, m is 1 or 2 and p is 0 or 1, with the provisos that m + p is 2 or less and the molar ratio of said alkoxysilane (i) to said silane coupling agent (ii) is 0.5:1 to 3:1; and (iii) a polyisobutylene polymer. Preferred emulsions of the invention further comprise a wax component.

Description

[0001] This invention is directed to the treatment of cellulosic and masonry surfaces. More particularly, it uses certain organosilicon compounds in combination with polyisobutylene, and preferably a wax, to render such surfaces water repellent.

[0002] US Patent 5,073,195 discloses an aqueous solution formed by combining water, a silane coupling agent and an alkoxysilane. This solution is then used as a treating agent for cellulosic and masonry surfaces for rendering such surfaces water repellent. An improvement on that disclosure is claimed in US Patent 5,300,327. Therein, a petroleum or synthetic wax is combined with the aforementioned silanes to provide an improved water repellency to wood or masonry. To achieve the most desirable results, an aqueous silicone resin emulsion is also included in the compositions taught by the latter patent.

[0003] Our invention relates to compositions and methods of treating cellulosic or masonry surfaces with aqueous emulsions of a combination of one or more alkoxysilanes, an amine or quaternary ammonium functional silane coupling agent and a polyisobutylene polymer. We have found that the water exclusion and water repellency of surfaces treated with our composition is superior to those treated, either with the above mentioned silane combination alone or with the polyisobutylene polymer alone. Furthermore, when our aqueous emulsion also includes a wax, such as a blend of petroleum and synthetic hydrocarbon waxes, cellulosic or masonry surfaces treated therewith exhibit water beading, which is a characteristic prized in many consumer-oriented applications. The latter compositions have imparted high, initial water exclusion and reduced water swell to wood treated therewith. These indicia of water repellency were also retained after subsequent exposures to moisture. Such a combination of initial and sustained water repellency is an unexpected result as compared to the prior art.

[0004] A composition of the present invention is in the form of an aqueous emulsion of (i) at least one alkoxysilane; (ii) at least one amino or quaternary ammonium functional silane coupling agent; and (iii) a polyisobutylene polymer or oligomer.

[0005] Component (i) of the invention is an alkoxysilane, or mixture of alkoxysilanes, of the general formula R_nSi(OR')_4-n wherein R is independently selected from the group consisting of alkyl radicals having 1 to 10 carbon atoms, preferably 1 to 6 carbons, alkenyl radicals having 2 to 8 carbon atoms, phenyl, chloropropyl and trifluoropropyl, n is 1 or 2 and R' is an alkyl radical having 1 to 6 carbon atoms. It is preferred that both R and R' are methyl radicals.

[0006] Suitable alkoxysilanes are compounds such as methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltributoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isobutyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diisobutyldimethoxysilane, phenyltrimethoxysilane, dibutyldiethoxysilane and dihexyldimethoxysilane.

[0007] Component (ii) is a silane coupling agent of the formula R''_mR'''_pSi(OR')_4-m-p wherein R'' is selected from the group consisting of amino or quaternary ammonium organo-functional groups, R''' is an alkyl radical having 1 to 4 carbon atoms, R' has its previously defined meaning, m is 1 or 2 and p is 0 or 1, with the proviso that m + p is 2 or less. It is preferred that R' is a methyl radical, R'' is selected from N-(2-aminoethyl)-3-aminopropyl or 3-aminopropyl groups and R''' is a methyl radical. For component (ii), the counterion, typically a bromide or chloride ion, is not explicitly shown for the case when R'' is a quaternary ammonium organofunctional group.

[0008] Suitable silane coupling agents with amino organofunctionality are N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(aminoethylaminomethyl)phenethyltrimethoxysilane, bis(2-hydroxyethyl)-3-aminopropyltrimethoxysilane, trimethoxysilylpropyldiethylenetriamine and 3-aminopropylmethyldimethoxysilane.

[0009] Suitable silane coupling agents with quaternary ammonium organofunctionality are compounds represented by the following formulas, wherein the counter ion is now explicitly shown and Me, Et and Ph hereinafter denote methyl, ethyl and phenyl radicals, respectively:
(MeO)₃SiCH₂CH₂CH₂N⁺(Me)₂C₁₈H₃₇ X⁻
(MeO)₃SiCH₂CH₂CH₂N⁺(Me)₂C₁₀H₂₁ X⁻
(MeO)₃SiCH₂CH₂CH₂N⁺(Me)₃ X⁻
(MeO)₃SiCH₂CH₂CH₂N⁺(Me)₂C₄H₉ X⁻
(MeO)₃SiCH₂CH₂CH₂N⁺(Me)₂CH₂Ph X⁻
(MeO)₃SiCH₂CH₂CH₂N⁺(Me)₂CH₂CH₂OH X⁻
(MeO)₃SiCH₂CH₂CH₂N⁺(Et)₃ X⁻
(MeO)₃SiCH₂CH₂CH₂N⁺(Ph)₃ X⁻
(EtO)₃SiCH₂CH₂CH₂N⁺(Me)₂C₁₈H₃₇ X⁻
(MeO)₃SiCH₂CH₂CH₂N⁺(Me)₂CH₂CH₂O-C(O)C(Me)=CH₂ X⁻ and
(MeO)₃SiCH₂CH₂CH₂N⁺ (Me)₂CH₂CH₂CH₂NHC(O) (CF₂)₆CF₃ X⁻,
in which the counterion X is either Br or Cl. Of these, the structure (MeO)₃SiCH₂CH₂CH₂N⁺(Me)₂C₁₈H₃₇Cl⁻ is preferred.

[0010] For the present invention, silanes (i) and (ii) are employed in a molar ratio of 0.5:1 to 3:1, respectively, preferably in a ratio of 1:1 to 1.5:1. These silanes may be introduced as a cold blend, but are preferably reacted with limited water (i.e., less than stoichiometric) to form a partial hydrolyzate. This partial hydrolyzate contains an alcohol (i.e., R'OH) formed as a byproduct of the hydrolysis reaction and may be used to form the emulsion of the invention, described infra, without further modification. Alternatively, the alcohol may be stripped out prior to preparation of the emulsion when a composition having a low VOC content is desired.

[0011] When the alkoxysilane is reacted with a silane coupling agent containing a reactive amino group or quaternary ammonium group, the reaction product may then be cold blended with another silane coupling agent having either an amino or quaternary ammonium reactive organofunctional group, if desired.

[0012] Component (iii) of the invention is a polyisobutylene polymer or oligomer having a number average molecular weight (Mn) of 200 to 2,300, preferably less than 1,500 and most preferably less than 1,000. Such polymers and oligomers are known in the art and many are available commercially in a variety of molecular weights and end group combinations. It has been found that the relatively low molecular weight of polyisobutylenes (i.e., Mn < 1,000), having terminal groups which can hydrogen bond to the hydroxyl groups generally found on cellulosic or masonry substrates, provide particularly superior water repellent treatment compositions in accord with the present invention. Thus, the preferred polyisobutylene polymers have at least one terminal group which contains a functional group such as epoxy, halide, alkoxyphenylene, hydroxyl, carboxyl, chlorosilyl, isocyanato, amino or amido. A highly preferred end group is epoxy. Again, these specific polymers and oligomers can be prepared by methods known in the art.

[0013] To form the compositions of this invention, an aqueous emulsion of components (i) through (iii) is formed by methods well known in the art. For example, an aqueous emulsion of the polyisobutylene may first be prepared by mixing this component with water and a sufficient amount of a non-ionic or anionic surfactant, and then by subjecting this combination to high shear, as in a homogenizer or sonolator, to result in a stable emulsion. This emulsion is then thoroughly mixed with components (i) and (ii) or, preferably, the above mentioned partial hydrolyzate of (i) and (ii). For the purposes herein, from 10 to 300 parts by weight of component (iii) is used for each 100 parts of the combined weights of component (i) and (ii) employed. Preferably, from 30 to 150 parts of (iii) are used for each 100 parts of (i) plus (ii). The above proportions are taken on a solids basis (i.e., active ingredients, excluding solvent and water). The aqueous emulsion so formed contains from 5 to 25 percent by weight (solids basis) of the combination of alkoxysilane (i), silane coupling agent (ii) and polyisobutylene (iii), preferably from 7.5 to 25 weight percent.

[0014] In preferred embodiments, and where water beading on the treated surface is desired, a wax (iv) is added to this emulsion. This can be accomplished, for example, by first preparing an aqueous emulsion of the wax and adding this to the emulsion of components (i) through (iii), although the order of mixing is not critical. Component (iv) is preferably carnuba wax or a blend of petroleum and synthetic waxes, more particularly a blend which includes both paraffin and polyethylene waxes. The polyethylene waxes can be high or low density polyethylene waxes or mixtures of high and low density polyethylene waxes. An exemplary wax and a wax found to be especially suitable in accordance with the present invention, is JONWAX® 120, a product and trademark of S.C. Johnson & Sons Inc., Racine, Wisconsin USA. This wax is sold in the form of an aqueous emulsion of polyethylene and paraffin waxes with a solids content of about thirty-five percent. Other blended paraffin and polyethylene type waxes can also be employed.

[0015] When included in our compositions, the wax (iv) is added at a level of 5 to 1,500 parts by weight for each 100 parts of the combined weights of components (i) and (ii), preferably 200 to 600 parts by weight. When the wax is included in the compositions of the invention, the total solids content of the emulsions should be 7.5 to 30 percent by weight, preferably 7.5 to 15 weight percent.

[0016] The emulsion compositions of this invention find utility as water repellent treatments for cellulosic and masonry surfaces and may be used in a manner similar to that described in the prior art and as illustrated in the examples. Thus, they may be applied by brushing, pouring, spraying, roller coating, dipping or doctor blading techniques. After application to a given substrate in an amount sufficient to thoroughly coat the surface thereof and impart a water repellent character thereto, our composition is preferably cured by exposure to ambient moisture for several days. Optimum amounts and cure conditions are readily determined by routine experimentation by one skilled in the art.

[0017] The following examples are presented to further illustrate the composition and method of this invention. All parts and percentages in the examples are on a weight basis and all measurements were obtained at 25°C., unless indicated to the contrary.

[0018] Aqueous emulsion treating compositions were prepared by blending the components shown in the second column of Table 1 at the indicated solids levels. The components used were as follows:

[0019] MTMS/AFS is a partial hydrolyzate prepared by reacting 36 parts of methyltrimethoxysilane (MTMS) and 58 parts of N-(beta-aminoethyl)-gamma-aminopropyltrimethoxysilane (AFS) (i.e., molar ratio of MTMS:AFS = 1.5:1) with 6 parts of water while maintaining the temperature below 50°C. and stripping out the by-product methanol.

[0020] Jonwax® 120 is a product of S.C. Johnson & Sons Inc., Racine, Wisconsin USA and is described as a water emulsion of polyethylene and paraffin waxes with a solids content of about thirty-five percent.

[0021] The abbreviation "PIB" represents various polyisobutylene (also referred to as polybutene) products of the Amoco Chemical Company, Chicago, IL. Thus, E-6 is described as an epoxy-terminated PIB having a Mn of 365. Likewise, E-16 is described as an epoxy-terminated PIB with a MN of 975. E-23 is described as an epoxy-terminated PIB with a Mn of 1,433. L-14 is described as a vinyl-terminated PIB with a Mn of 300.

[0022] In the examples, the PIB was first emulsified by running a mixture of 55% PIB, 42% deionized water and 3% Tergitol® TMN-6 {trimethylnonylphenyl poly(ethylene oxide); Union Carbide Chemical & Plastics Division, Danbury, CT} through a microfluidizer until a constant particle size was achieved (at least 4 passes).

[0023] The MTMS/AFS hydrolyzate, Jonwax® 120 emulsion and PIB emulsion were blended and diluted with water to provide the treatment emulsions shown in Table 1. It was noted, however, that the partial silane hydrolyzate alone formed a solution when so diluted rather than an emulsion at the 2.5% solids concentration employed (Example 1).

[0024] The emulsions of Table 1 were used to treat wood samples which were then subjected to water repellency testing according to two different procedures, as described infra.

[0025] Water repellency using a "Swellometer" Test for wood, according to Federal Specification TT-W-572B, employed wafers cut from straight grained, clear, average density, flat grained, kiln dried, ponderosa pine sapwood. The wood was machined to a cyclinder of 1.5 inches by 10 inches (38.1 by 254 mm) and wafers having a thickness of 1/4 inch (6.4 mm) were cut therefrom. All wood pieces were conditioned at 50% ± 5% relative humidity and 21.1° ± 2.8°C. until a constant weight was reached. An untreated sample, selected from a consecutive piece of the wood in each case, served as a control for each treated sample. Treated pieces were soaked for three minutes in the water-based repellent compositions and then air dried at ambient conditions for one day, whereupon said samples were returned to the conditioning room for six days. When a sample thereafter attained constant weight, it was further tested for swell in a Swellometer (basically, an apparatus for the precise determination of change in length of the sample) in accordance with American Society for Testing and Materials (ASTM) Standard 4446-84. Treated and untreated pieces were placed in Swellometers and submerged in deionized water for thirty minutes. The swell of each piece of wood was recorded after a 30 minute soak period. The percent swell in the longitudinal direction (%WS) was calculated as: 100 X (swell control - swell treated piece)/(swell control). These values are reported in the fourth column of Table 1. It should be apparent that the value for the untreated controls is zero by definition, this being applicable for all the similarly calculated results relating to Swellometer and Gravimetric testing described infra.

[0026] In addition, the Swellometer samples were weighed before and after the above described water exposure and the water exclusion relative to control samples (%WE) was calculated as: 100 X (wt. control - wt. treated piece)/(weight control). These values are reported in parentheses in the fourth column of Table 1. The above %WS and %WE values represent initial swell and water exclusion values and are designated as "TEST I" in Table 1. In a variation, the above testing was continued by allowing the samples to equilibrate at 50% humidity for an additional week. The 30 minute soak was repeated and the %WS and %WE values again determined (TEST II in Table 1). This was repeated yet a third time (TEST III in Table 1) if the variation between TEST I and TEST II was significant (i.e., if the measurements differed by at least 10%).

[0027] In a gravimetric water absorption test method, standard 2 X 4 inch (50.8 x 101.6 mm) knot-free pine boards were cut into six inch (152.4 mm) lengths and allowed to equilibrate in a 50% relative humidity atmosphere. The boards were treated with the water repellent composition by either brushing until they were saturated or by soaking the boards in the composition for three minutes. The treated boards were allowed to cure for one day at ambient conditions and allowed to float in the 50% humidity room for six days to completely cure and condition the sample. An untreated control board was kept in a fifty percent humidity room during the cure process. After cure, the boards (including the control board) were weighed and placed in room temperature water for 15 minutes, turned over and allowed to float in the water for an additional 15 minutes. All of the boards were weighed and the water uptake was calculated (TEST I). The percent water exclusion was computed as the water uptake of the control board minus the water uptake of the treated board, multiplied by one hundred and divided by the water uptake of the control board. The results of this procedure are presented in the last column of Table 1, wherein data of repeat testing after additional conditioning for one week at 50% humidity (TEST II) and additional conditioning for yet another week (TEST III) are also presented.

[0028] It is seen from the above table that our compositions provide improved water exclusion or water swell (i.e., larger values of WE%, WS% of the Swellometer test and % exclusion of the gravimetric test) than the silane mixture alone, the wax alone or the PIB alone. Furthermore, higher initial values of %WS and %WE were obtained for compositions of the invention containing wax (Examples 7 and 8) relative to a comparable composition (Example 5) which did not contain PIB. Additionally, these values did not drift much from the initial data when the tests were repeated (i.e., TEST II, etc.).

[0029] The emulsion composition of Example 7 was used to treat sandstone and mortar samples by Federal Test Method SS-W-110C to compare water absorption relative to untreated samples which were maintained at ambient conditions. Mortar samples were in the form of cubes, two inches (50.8 mm) on a side; sandstone samples were 1 X 1 X 4 inch (25.4 x 25.4 x 101.6 mm) Briar Hill Sandstone pieces. The mortar and sandstone pieces were wire-brushed and blown clean with high pressure air.

[0030] Sandstone samples were treated by dipping in the emulsion composition for 10 seconds followed by cure at ambient conditions. Weighed sandstone samples (treated and control) were soaked in a tray containing water to a depth of 1/4 inch (6.4 mm), re-weighed and the water exclusion (%WE), relative to untreated control, was calculated using an average of three determinations: (%WE) = 100 X (wt. control - wt. treated piece)/(weight control). When the above cure time was 2 days and the soak time was 72 hours, the value of (%WE) was 12.4%. In comparison, after cure for 7 days and soak for 72 hours, this value was 14.6%. When the above samples were dried at ambient atmosphere for 10 days and re-tested by soaking for 96 hours, the (%WE) was 95.6%. Similarly, when these samples were dried at ambient atmosphere for 2 days and re-tested by soaking for 72 hours, the (%WE) was 66.5%.

[0031] Mortar samples were treated in a similar manner, but required longer dip times to obtain satisfactory water repellent character (i.e., dipped repeatedly until 4 grams of treatment composition were absorbed by the sample). After a 7 day cure and a 72 hour soak, the (%WE) was 44.8%.

Claims

1. An aqueous emulsion comprising:
   (i) an alkoxysilane of the formula R_nSi(OR')_4-n wherein R is selected from the group consisting of alkyl radicals having 1 to 10 carbon atoms, alkenyl radicals having 2 to 8 carbon atoms, phenyl, chloropropyl and trifluoropropyl, n is 1 or 2 and R' is an alkyl radical having 1 to 6 carbon atoms; (ii) a silane coupling agent of the formula R''_mR'''_pSi(OR')_4-m-p wherein R'' is selected from the group consisting of amino or quaternary ammonium organofunctional groups, R''' is an alkyl radical having 1 to 4 carbon atoms, R' has its previously defined meaning, m is 1 or 2 and p is 0 or 1, with the proviso that m + p is 2 or less and the molar ratio of said alkoxysilane (i) to said silane coupling agent (ii) is 0.5:1 to 3:1; and (iii) a polyisobutylene polymer, wherein from 10 to 300 parts by weight of said polyisobutylene polymer (iii) are used for each 100 parts by weight of said component (i) plus component (ii).

2. The emulsion of claim 1 further comprising (iv) a wax, wherein from 5 to 1,500 parts by weight of said wax (iv) are used for each 100 parts by weight of said component (i) plus component (ii).

3. The emulsion according to claim 2 wherein said wax (iv) is a blend of petroleum and synthetic waxes.

4. The emulsion according to claims 1 - 3 wherein n of said alkoxysilane (i) is 1, m of said coupling agent (ii) is 1 and R' of components (i) and (ii) is methyl.

5. The emulsion according to claim 4 wherein R of said alkoxysilane (i) is an alkyl group having 1 to 6 carbon atoms and R'' of said coupling agent (ii) is selected from N-(2-aminoethyl)-3-aminopropyl group or 3-aminopropyl group.

6. The emulsion according to claims 1 or 2 wherein the number average molecular weight of said polyisobutylene (iii) is less than 1,000.

7. The emulsion according to claim 6 wherein said polyisobutylene (iii) has at least one epoxy terminal group and the R group of said alkoxysilane (i) is methyl.

8. A method for treating a surface to render said surface water repellent, said method comprising applying to said surface the emulsion of claims 1 or 2.